Television broadcasts including a commercial message broadcast are broadly divided into a “program main part broadcast” and a “commercial message broadcast” on the basis of their contents. In the case of a movie program, the program main part broadcast is a broadcast portion based on the video audio data of a movie content itself. On the other hand, the commercial message broadcast is a broadcast portion based on the video audio data supplied by a client such as an advertiser, an advertisement agent, or the like, who exchanges contracts with a broadcasting company. Furthermore, the commercial message broadcast includes a broadcast portion which is broadcasted by a broadcasting company in order to advertise and publicize its own company. The commercial message is generally abbreviated to CM, thus, it is also referred to as CM in the present application hereinafter.
This CM broadcast is generally produced with video and audio managed to attract viewer's attention in order to appeal an advertising claim effectively within a limited short period of such as fifteen seconds or thirty seconds. One of the ways is to start with music and a line of advertisement in a loud volume from the beginning of the CM broadcast.
However, it is considered that the scheme of the CM broadcast may provide a viewer who has concentrated on watching a program main part broadcast with displeasure at the CM broadcast which does not have anything to do with the content of the program main part broadcast suddenly starting with a loud volume. A volume of the CM broadcast may be heard considerably loud in the case of actually producing the CM broadcast with a louder volume than the program main part broadcast, or in the case where a scene immediately before switching to the CM broadcast is quiet because a dynamic range of a volume in the program main part broadcast is wide.
Therefore, a technique of lowering a volume by identifying with high precision a sudden loud volume of the CM broadcast or the like which gives a viewer displeasure is necessary in order to reduce a loud volume heard when switching from the program main part broadcast to the CM broadcast.
A conventional television receiver has detected an audio scheme of a television broadcast, and automatically discriminated a program main part and a CM broadcast to perform a volume control for lowering (e.g., lowering by 2 decibel) a volume only during the CM broadcast section (Patent document 1).
Another conventional television receiver has created database inside a digital broadcast receiving device for each CM broadcast program, and determined whether it is CM or not in real time when receiving a broadcast (Patent document 2). Further, another conventional television receiver has been provided with a CM discriminating means for using a result of a sound multiplex discriminating means for discriminating a stereophonic broadcast in a sound-multiplex broadcast to give a weight on a discriminating element of the CM broadcast (Patent document 3).    Patent document 1: Japanese Patent Application Laid-Open No. 2002-112174 (page 4, FIG. 1)    Patent document 2: Japanese Patent Application Laid-Open No. 2003-143544 (page 7, FIG. 1)    Patent document 3: Japanese Patent Application Laid-Open No. 2002-077770 (page 6, FIG. 1)
The television receiver according to Patent document 1 focuses on that an audio scheme of the CM broadcast tends to be a stereophonic broadcast, and discriminates the program main part which tend to be a monophonic broadcast or a bilingual broadcast and the CM broadcast. However, in a recent analog broadcast program and digital broadcast program such as a ground analog broadcast and BS/CS satellite broadcast, the program main part tends to be a stereophonic broadcast, so that it is getting difficult to identify the CM broadcast with preferable precision by the television receiver according to Patent document 1.
The television receiver according to Patent document 2 once stores a CM broadcast received for determining the CM broadcast inside the television receiver as CM data, and needs to determine a CM broadcast section on the basis of the CM data, so that a configuration of a discriminating process of the CM broadcast would be complicated.
Furthermore, the television receiver according to Patent document 3 combines conditions such as information of a broadcasting company of a guide channel or the like in addition to determination of an audio state to comprehensively discriminate whether it is the CM broadcast or not, so that a configuration of a discriminating process of the CM broadcast would be complicated.